Do Koi Hibernate? How To Care For Them Over Winter

Is your koi fish immobile or staying in one position in the tank? Are you scared your fish is dead or has any health problems due to its motionlessness? Or you don’t know when koi fish are in a hibernation state? You will get enough details about koi fish hibernation in this article.

Koi fish usually go into hibernation when the water temperature goes below 40 degrees F. They will have reduced metabolism and become dormant during this time. It allows them to regulate their body temperature, thereby ensuring their survival in water when temperature close to freezing.

Do Koi Hibernate

At What Temperature Do Koi Hibernate?

Koi fish hibernate when the water temperature starts getting lower than 40 degrees Fahrenheit. They hibernate at a temperature slightly above freezing point. And will not survive when the water freezes.

If part of the tank or pond freezes and some other parts are still in the liquid state, they will hibernate and maintain their good health status when the state phases-out.

They start experiencing reduced metabolism when the water temperature starts to fall to about 50 degrees Fahrenheit. When the temperature gets to this state, you might have to reduce their feeding rate to about 2 to 3 times weekly. As the water progresses below 50 degrees, you have to reduce the feeding according to your discretion.

When the water temperature gets to 40 degrees Fahrenheit, you should stop feeding them. They will be in the hibernation state. At this stage, the koi fish does not respond to most of the water changes. You also have to maintain good water quality when your koi fish is in a hibernation state.

How Do I Keep My Koi Pond Warm in the Winter?

Keeping your koi pond warm in winter can be the exact thing you need to do to keep your fish alive. There are several ways you can keep the pond warm for your koi fish. One of the most common ways of keeping your pond warm is using a heater.

Heaters will help you raise the temperature of your water and keep it from freezing. The rate at which the heater increases the water temperature depends on the size of the pond. You have to be careful when using heaters so as not to overheat your pond.

Another way to keep your koi pond from freezing is to make use of a de-icer. The de-icer will prevent the freezing of your pond water thereby ensuring the safety of your koi fish. If you want to make sure your koi pond does not freeze, the de-icer is a good option.

During winter, turning off the water pump and several other water features will help you keep the water from freezing. Water pump, water filter, fountain, etc. exposes the water to cold air causing it to get cold quickly. It increases the risk of getting the water frozen. You have to turn off these features to save your Koi fish from freezing.

Another way is to keep the pond deep enough to withstand the cold water. You have to make the pond water at least 4 feet deep to ensure the water quickly gets frozen.

If the pond is very deep, the highest that gets frozen is the surface and middle layer. Hence, keeping the koi fish safe at the tank’s bottom.

You can also provide proper aeration for your koi fish in the tank. Proper aeration will perform double work. First, it will ensure there is enough oxygen in the pond. Secondly, it will keep the water temperature high to prevent freezing.

You can also make use of surface heaters to keep the water in the pond warm.

When to Stop Feeding Koi Fish at Winter

Koi fish experience reduced metabolism, especially when the water temperature is low. The reduced metabolism causes the fish not to eat much. So, it’s best to feed them about 2 to 3 times weekly when the temperature gets below 50 degrees Fahrenheit.

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When the temperature goes below 40 degrees Fahrenheit, you should stop feeding the koi fish as they will already be in a hibernation state.

You also have to make sure you fulfill some other requirements when you stop feeding the fish. This is because in a hibernation state, they are prone to danger and risk. You have to provide protection to your fish and make sure it is safe during this period.

How Long Do Koi Fish Go Without Eating During Winter

Koi fish can easily survive without food for about two weeks or more. During winter, they can survive without food for months. If you maintain optimum environmental conditions and provide the necessary requirements, they will survive through winter in good health.

For your koi fish to survive the winter, you have to make sure you keep the water quality intact. You also need to feed your fish well before winter arrives. Also, before winter, you should feed your fish with fatty and protein-rich foods.

Koi fish store fat before the arrival of winter. So, it uses the stored fat to supplement the needed food for the winter period.

When the temperature is not very low, you should feed the Koi fish with food to sustain them throughout the winter. Your koi fish will last the winter without food if you take the proper steps.

When to Start Feeding Koi Fish After Winter

Your human feelings and affection will want you to feed your koi fish immediately after winter. This is because you feel they have been starved all this while. But it might not be good enough to feed them straight away.

You need to wait for the water to warm up before feeding them. You can also heat the water to about 48 degrees Fahrenheit before giving your Koi fish any food.

You can start the filtration system and pump before you begin feeding them properly. Start by feeding them gradually before going back to their former feeding routine.

What Do Koi Do in the Winter?

During winter, the koi fish go into hibernation known as torpor. Torpor is a form of hibernation that animals experience due to temperature changes.

The hibernation causes the koi fish to become almost motionless, making them conserve energy and resources. When the water becomes too cold for your koi fish during the winter, they go into this hibernation mode.

What Do Koi Do in the Winter

The koi fish also experience reduced metabolism as their immune system and other bodily functions change. They will stop eating when the temperature becomes lower and use the fats they stored before winter. Koi fish will be at their most gentle state during winter.

Can You Keep Koi Fish Outside in Winter?

You can keep your koi fish outside during winter, provided you give them what they need. You have to make sure the pond is at least 4 feet deep. So, the water does not get frozen entirely when the winter temperature gets intense.

You also have to cover the pond to protect the koi fish from predators as they will be dormant and unable to protect themselves. Using a heater might help too.

Can Koi Fish Freeze and Come Back to Life?

Koi fish cannot survive after they get frozen in ice. They can survive when the pond becomes cold or even if parts of the water freezes. But if all the water freezes and traps the koi fish, they cannot survive this condition.

This is why you have to ensure your koi fish is safe during the winter. You have to prevent the water from getting completely frozen.


Koi fish will hibernate when the water temperature gets low. The hibernation occurs mainly during winter, causing the Koi fish to exhibit some changes in its body function. You have to take care of the fish during this period to ensure its good health and safety.